(1) Field of the Invention
The present invention relates to a printing apparatus for forming solder balls on an electrode of a substrate such as a semiconductor by a printing method, and particularly to a solder ball printing apparatus for printing using solder balls.
(2) Description of the Related Art
In a conventional solder ball printing apparatus, there have been proposed various configurations in which a mask used for printing solder balls is placed on a substrate such as a semiconductor, the solder balls are fed onto a mask surface, and the fed solder balls are pressed from an opening area provided at the mask into a surface of the substrate such as a semiconductor.
As described in, for example, Japanese Patent Application Laid-Open No. 2005-101502, there is disclosed a printing apparatus configured in such a manner that a solder ball feeding unit for feeding solder balls onto a mask surface and a plurality of wire members provided at a sieve are moved in the horizontal direction while being pressed into the mask surface in order to press the solder balls fed onto the mask surface into a surface of a substrate from an opening area provided at the mask.
In the printing apparatus, it is described that at a left end of the mask, there is provided a solder ball sucking port where the solder balls remaining on the mask surface are sucked and removed.
Further, Japanese Patent Application Laid-Open No. 2008-142775 discloses that when solder balls are squeezed into an opening area of a mask by moving a squeegee head in the horizontal direction while rotating the same, a predetermined amount of solder balls is fed to a rotational shaft portion of the squeegee head from a measuring unit provided at an upper portion of the squeegee head, and the solder balls are fed from the rotational shaft onto a mask surface.
In the configuration of Japanese Patent Application Laid-Open No. 2005-101502, when the mask is placed on a table, a solder ball feeding apparatus is disposed at an inlet port to which the mask is carried, and the mask is moved on the mask while feeding the solder balls onto the mask surface from the solder ball feeding apparatus.
Accordingly, the solder balls are uniformly dispersed and arranged on the mask surface. Thereafter, the sieve is moved in the horizontal direction, and the solder balls are fed into the opening area of the mask. When the solder balls are dispersed and arranged on the mask in this method, there is a risk that the dispersed and arranged solder balls vary in amount due to fluctuations caused when the mask is moved and oscillation when the movement of the mask stops.
Further, since the solder balls are fed before the mask is set in the printing apparatus, it is necessary to move the mask for each printing process, resulting in the problem of a long tact time.
Further, solder balls unused in printing are sucked through the sucking port provided separately from a solder ball feeding head. In this case, when the extra solder ball can not be held by the first wire member of the sieve in a wire shape, the extra solder ball is held by the subsequent wire member to be carried near the sucking port. However, there is a possibility that the solder ball held by the subsequent wire member and the solder ball which is previously fed are fed to an opening area of the mask at the same time.
In the method of feeding the solder balls onto the mask surface from the rotational shaft portion as disclosed in Japanese Patent Application Laid-Open No. 2008-142775, the solder balls are dispersed and arranged on the mask surface along with the rotation of the squeegee head. Accordingly, the solder balls can not be always uniformly dispersed and arranged, and printing defects are generated. Thus, a repairing step is essential.
As described above, when the solder balls are dispersed and arranged on the mask, there is a risk that the dispersed and arranged solder balls vary in amount due to fluctuations caused when the mask is moved and oscillation when the movement of the mask stops. In addition, since the solder balls are dispersed and arranged on the mask surface along with the rotation of the squeegee head, the solder balls can not be uniformly dispersed and arranged. Thus, there are problems in aspects of the configuration of the apparatus and printing methods.
Accordingly, a first object of the present invention is to provide a solder ball printing apparatus for uniformly printing solder balls with a high degree of accuracy.
A second object of the present invention is to provide a solder ball printing apparatus for shortening a tact time in solder ball printing.
A third object of the present invention is to provide a small-sized solder ball printing apparatus with a simple configuration.
A fourth object of the present invention is to provide a solder ball printing apparatus in which solder balls unloaded into an opening area of a mask are collected for reuse by solder ball rotating and collecting mechanisms.
A fifth object of the present invention is to provide a solder ball printing apparatus in which when solder balls are fed to a solder ball shaking and discharging unit from a solder ball reservoir unit, the solder balls are reliably fed to the solder ball shaking and discharging unit while preventing the solder balls from being spread around.
A sixth object of the present invention is to provide a solder ball printing apparatus which reduces a period of time when solder balls are exposed to the atmosphere to prevent the solder balls from being oxidized.